Flame detector



Nov. 24, 1953 J. A. DEUBEL 2,660,645

FLAME DETECTOR Filed Sept. 20, 1950 3 Sheets-Sheet 1 INVENTOR. 54 JUSTIN A. DEUBEL BY M L W ATTORNEYS J. A. DEUBEL FLAME DETECTOR Nov. 24, 1953 3 Sheets-Sheet 2 Filed Sept. 20, 1950 INVENTOR. JUST/N A. DEUBEL m L fi AT TURNEYE:

J. A. DEUBEL FLAME DETECTOR Nov. 24, 1953 Filed Sept. 20, 1950 3 Sheets-Sheet 5 INSULATION INSULATIUN INVENTORF mam A. DEIJEyE-L J 2, /ufilffi m ATTORNEYS Patented Nov. 24, 1953 UNITED STATES asserts PTENT OFFICE FLAME DETECTOR ration of Wisconsin Application September 20, 1950, Serial No. 185,797

8 Claims.

Ihis invention relates to a control mechanism that serves to open. and close an associated electrio circuit in accordance with external condi tions which influence the operating mechanism.

More particularly this invention concerns a novel type of switch that operates in response to temperature changes which has application as a flame responsive switch in an oil burner control apparatus.

In an oil burner operation it is of prime importance to provide sufficient and adequate safety devices to prevent burner operation under ad normal conditions. One of these safety requirements necessitates the use of a control that will stop burner operation upon failure to initiate combustion. Generally some type of flame responsive device has in the past been used to determine the presence or absence of flame, and these devices are usually located remotely from the burner and burner primary control. ever, many of these devices now in use are subject to limitations in rapidity of response and length of useful life. Many factors contribute to cause these limitations but the most important one is the necessity of positioning the flame responsive device in proximity to the flame. The deteriorating effects of the flame, the temperature and pressure of the air stream, vibration etc. require a construction that will be relatively unaffected by these factors. This invention embodies a type of construction that effectively shields the moving parts from the flame and products of combustion, provides positive and immediate response to reversals in temperature change, and permits ease of adjustment and repair, and is located within the burner blast tube and therefore can be assembled with the burner and primary control as a unit.

A further feature of the invention resides in the slip-friction element which permits over travel of the actuating member in both directions and provides immediate response upon reversal of the direction of temperature changes.

Further objects will become apparent as this description proceeds and will be particularly pointed out in the appended claims.

In the following description like reference characters indicate like parts in the several drawings: I

Figure 1 represents a side view of the flame or heat responsive switch with a portion of the side plate, removed.

Figure 2 represents a top view of the name or heat responsive switch with a portion of the top plate removed.

l-low- Figure 3 represents a top view of the switch mounting.

Figure 4 represents an end view of the switch mounting.

Figure 5 represents a perspective view of the end portion of an oil burner tube assembly with the flame detector mounted in a preferred location.

Figure 6 represents a perspective view of the assembled switch and mounting.

Figure 7 represents a front View of the switch contact fork.

Figure 8 is a view, similar to Fig, 1, showing a modification of the device of Fig. 1.

Fig. 9 is a perspective View of the switch mounting.

Fig. 10 is an enlarged end View of the switch mounting, similar to Fig. 4.

Fig. 11 is a composite view of the prong-=receiving end assembly.

In respect to comparative sizes in the several figures, the Figs. 1, 2, 3, 4, 6, 7, and 8 are drawn to approximately twice actual size and the flame responsive device of Fig. 5 is drawn to actual size.

Referring now to Figs. 1 and 2 in which is shown the flame or heat responsive switch unit It) having a casing ll, substantially rectangular in shape, encompassing the side, top and bottom with the ends left open. A rectangular cupshaped closure member I2 is securely fastened within the open end of easing H. The member I2 has an open end I 3 and a closed end is sealing' off the opening is from the remainder of casing Ii. The member 12 is formed of metal or other heat conductive material and is the primary recipient of heat radiation from th flame. A heat responsive member comprising a bimetallic strip 55, serving as an actuating member, is securedby welding or other suitable means to the closed end is. This arrangement places the bimetal 15 in heat conductive relationship with the cup member it. In this arrangement, the

free end 20 of bimetal I5 is securely fastened to a channelled lever 16. The lower ends it of the flanges of channel-shaped lever i 6 are perforated to receive a pivot pin I8 secured in position by lock rings l9. A channel-shaped contact lever ii! is similarly supported on the pivot pin I8 but separated from lever It by friction washers such as carbon washers 22. A flexible contact blade 33ais fastened by any suitable means to the web-portion .33 of lever 2|. Circumferentially surrounding the pin l8 and interposed between the flanges of contact lever 2| is a compression spring 24. The spring 24 serves to spread the channel flanges against the carbon washers 22 which are confined by the ends I 1 and lock rings IS. The result of this arrangement permits unitary movement of levers H5 and 2| when such movement is unobstructed and also provides for slip frictional movement between levers l6 and 2| when the movement of lever 2| is obstructed.

Within the open end of easing is securely fastened an insulation piece 26 which effectively seals this end of casing Fastened to the piece 26 by rivets or other suitable means is an L- shaped, electrically conductive bracket 21. A contact prong 2B is secured to the bracket 21 and projects through a hole in insulation piece 126. A threaded aperture in the bracket 21 serves as a means of support and adjustment for a threaded contact member 29. A stop 3|, supported by a bracket 32 which is riveted to the piece 26, limits the counterclockwise movement of lever 2|. The contact 29 cooperates with the webportlon 33 of channel 2| to constitute a switch which may be integrated into the oil burner control system. Flexible blade 33a has a slight upward bias and therefore there is a small clearance between blade 33a and the portion 33 when the contacts are open, the blade 33c being flexed slightly downward when the contacts are closed. The amount of this press-back flexure of blade 33a determines the magnitude of the temperature increase necessary to open the contacts. The position of contact 29 with relation to the stop 3| is adjustable. This adjustment determines the amount of unobstructed clockwise movement of lever 2| which may take place upon a decrease in temperature of the strip l5 and consequently determines the magnitude of the temperature decrease necessary to reclose the switch contacts 29-33. As shown in the drawings, the stop 3| is not connected to any electrical circuit and serves solely as a stop, however, it could be utilized as an electrical contact. This could be accomplished by providing the bracket 32 with a prong similar to the prong 26 and an exterior connection to complete a circuit. The contact lever 2| would provide a common lead for both circuits. The device would then act as a double throw switch.

An upturned portion of the contact lever 2| provides an electrical terminal 34 to which a flexible conductor lead 35 is soldered or otherwise fastened. The lead 35 is passed over the spring 24, led along the base of channel i6 and fastened to the casing [I by soldering. This arrangement electrically grounds the lever 2| to the casing H to provide one path for current flow from the switch. Essentially a high resistance ground exists from lever 2|, through carbon washers 22, channel l6, bimetal I5, cup member 2|, and casing H but this path is undesirable for this application of the invention, in that current through the bimetal will generate heat and affect operation of the switch.

Referring now to Figs. 3-6 and 9 there is shown the switch mounting 36, comprising a mounting ocket 31 and a mountin cl mp 38. The clamp 38 is threaded to provide a tightening screw 33 which enables the mounting 36 to be secured to an oil tube 54 as shown in Fig. The mounting socket 31, formed of conductive metal, has an open flanged top 4| allowing insertion of flame responsive switch unit |6 into the mounting socket 31. An open end 42 of mounting socket 31 has inturned edges 43 and 44 which form a slotted receptacle in the mounting socket end. An inner insulation piece 45, a contact fork or receptacle 46 (Fig; 7), and an insulation piece 41 are assembled within this slotted portion, after which the edges 43 and 44 are squeezed together and bent over to form tabs 4|a to secure this assembly within the mounting socket 31. The insulation pieces 45 and 41 are made the same size as the end of the mounting socket 31. This assembly is more clearly illustrated in Figs. 9, l0, and 11 wherein the contact fork 46 is shown in relation to the insulation pieces 45 and 41. In Fig. 11 the insulation pieces 45 and 41 and the contact fork or receptacle 46 are shown in their aligned relationship prior to assembly in the slotted end of the mounting socket 31. The contact fork 46 (Figs. 7 and 11) adjacent its ends 56a and 501) provides an opening into which the contact prong 28 may be inserted upon assembling of the detector In and mounting 35. An L-shaped extension 48 of the fork 46 is attached to the central wire 49 of a metal sheathed conductor lead. This type of lead has the central hot wire separated from the grounded sheath 50 by insulation. The grounded sheath 50 is soldered to a projection 44a of edge 44 of mounting socket 31 (Fig. 6). Thus, when the unit [,0 is assembled within the mounting socket 31, the wire 49 is electrically connected to the extension 48, fork 46, prong 28, bracket 21 and contact 29. The grounded sheath 50 is electrically connected to the projection 44a, mounting socket 31, casing I, lead .35, terminal 34, and contact lever 2|. Fig. 6 shows the assembled flame detector 5| with the unit In inserted into the mounting socket 31.

Referring now to Fig. 5 in which is shown the blast-tube portion of a gun type oil burner having the flame detector 5| mounted on the oil tube 54. The blast tube 52 has an opening 53 through which the atomized mixture of oil and air is expelled into the combustion chamber of an oil-fired furnace. The oil tube .54 is provided with an orifice 55 from which the oil under pressure is injected into the air stream which flows inside the tube 52. Typical means provided for ignition purposes are the electrodes 56 with their corresponding insulators 51.

Note that the detector unit 5| is mounted on the oil tube 54 in such a position that the end l3 of cup member I2 is in proximity to the opening 53 to receive a maximum of radiated heat from the burner flame.

In operation, when the oil burner is shut down the strip l5 will be in its cold position and portion 33 will be in electrical contact with the contact 23. as shown in Fig 1. After the oil burner is placed in operation, heat from the flame will be radiated to the member l2, at its end l4. By conduction and radiation, heat will be transmitted to strip l5. Assuming the higher expansive side of the bimetal strip I5 is adjacent the member l2, the strip l5 will flex away from member I2 at its free end as its temperature increases. Upon the initial movement of the free end of strip IS, the member 16 and lever 2| will move as a unit, pivoting lever 2| counterclockwise about the pin l8. This movement, depending on the amount of press-back of blade 33a, soon separates contacts 23-33 indicating tothe burner control apparatus to which the flame detector is connected that combustion is taking place within the furnace combustion-chamber.

Continued increase in temperature of strip |5 moves the lever 2| into engagement with the stop 3|, which obstructs further counterclockwise movement of lever 2!. Further movement of strip l5 produces slippage at the carbon washers 22 After the burner has operated for the required period and the burner flame has been extin guished, the strip I5 will cool causing it to move its free end toward member I2. This movement will immediately result in lever 2| leaving the stop BI and moving into engagement with contact 29. This closure of contacts 29-33 indicates to the burner control apparatus that the burner flame has been extinguished and the combustion chamber is cooling. Further cooling of strip I5 will result in slippage at the carbon washers 22. Lever 2! will be held in a position such that an increase in temperature of strip is will immediately open the contacts 29-33.

Figure 8 shows a modification of the device previously described. In this modification, the switch is arranged so as to be closed when the bimetal strip H5 (comparable to strip 55 of Fig. 1) is in its hot position. This form of the flame detector has the contact assembly and the heat responsive element hermetically sealed within an outer casing I31.

The casing It! has a contact prong l28 mounted on its closed end. The prong I28 is sealed to an eyelet I60 by means of a globule ISI of fused glass, or similar material, and the eyelet Itil is fastened, by any suitable means such as solder, into an opening in the closed end of the casing I3'l. The inner end of prong I28 has a central, axial opening or recess in which is seated a compression spring I62.

The switch unit is composed of a frame or housing II I including a plate I26, formed of suitable electrical insulating material. Plate 25 has riveted to it a bracket I32 carrying a stop I3I. An electrically conductive rivet I63 fastens a contact carrying bracket I21 to the plate I26. When the flame detector is assembled the outer end of rivet I63 bears against the spring I62 which serves as an electrically conductive path between the contact I 29, mounted on the bracket I21, and prong I28. A contact carrying blade I2 Ia is fastened by any suitable means to a channel-shaped lever !2 I, the lever I2I and a member He being assembled on a pin II 8 by means of the slip-friction mechanism previously described. Member II 6 is mounted on the free end of strip II 5, which, in turn, is secured, by any suitable means to a cup-shaped member 5 I2. In assembling the flame detector, the

housing IIl including plate I26, upon which are mounted brackets I21 and I32, is inserted into casing E3], the head of rivet I63 seating against the end or spring I52, compressing it slightly. Member HE is then inserted into the casing I31, which in turn is inserted into a mounting socket 3'5 shown in i. The flanged edges of member H2 resting against the edges of casing I31, to which they may be soldered thereby hermetically sealing the assembly. It will be noted that because of the flexibility of spring I62, the position of plate 525 with reference to the closed oi casing is! is not critical, the compression of spring is: perrnittim slight variations in the length. dimensions of the casing I31, frame I i i, and member I :2. The resulting advantage in utilizing components which need not be manufactured to extremely close dimensional tolerances is obvious. Additionally, spring I62 insures that good electrical contact is maintained between prong I23 and contact I29. ihe operation of the modification of Fig. 8 is identical to 6 that previously described, except that the switch contacts are closed upon an increase in temperature and opened upon a decrease in temperature.

There have been illustrated preferred embodiments of the invention, but its scope is to be limited only by the appended claims.

What is claimed is:

1. A thermally responsive switch comprising switching means, a casing enclosing said switching means, a connector prong extending from one face of the casing and connected to said switching means within the casing, a mounting socket into which the casing may be removably inserted, the wall of the mounting sochet adjacent said prong being formed of insulating material and having an opening therein accommodating said prong, an electrically conductive member mounted within said well and having portions engaged by said prong when said casing is inserted into said mounting socket, said conductive member having a part extending outside said wall to provide an external lead-in connection for said switching means.

A switch assembly comprising an outer casan inner switch housing insertable into the casing, switching elements mounted within said housing, an electrica ly conductive member extending through a wall of said housing and electrically connected to said switch elements within said housing, electrical terminal means extending through a wall of said casing adjacent said conductive member, and flexible means extending between said terminal means and said conductive member and flexed an amount proportional to the depth of insertion of said housing into said casing, said flexible means also serving as an electrical connection between said terminal means and said conductive member.

3. A switch assembly comprisin an outer casing, an inner switch housing insertable into the casing, switching elements mounted within said housing, an electrically conductive member extending through a wall of said housing and electrically connected to said switch elements within said housing, electrical terminal means extending through a wall of said casing adjacent said conductive member, and. a compression spring extending between said terminal means and said conductive member and compressed an amount proportional to the depth of insertion of said housing into said casing, said compression spring also serving as an electrical connection between said terminal means and said conductive memher.

4. A switch assembly comprising an outer casing, an inner switch housing insertable into the casing, switching elements mounted within said housing, an electrically conductive member extending through a wall of said housing and electrically connected to switch elements within said housing, an electrical connector prong extending through a wall of said casing adjacent said conductive member, the outer end of said prong being adapted for connection to an external lead-in wire, the inner end of said prong halfing an axial recess therein, a compression spring bottomed within said recess and contacting said conductive member when said housing is inserted into said casing, said spring being compressed an amount proportional to the depth of insertion of said housing into said casing, said spring also serving as an electrical connection between said prong and said conductive member.

5. A hermetically sealed switch assembly adapted for mounting within the blast tube of an oil burner comprising: anopen-ended outer casing, switch elements mounted within casing, a closure member for the open end of said casing adapted to receive radiant heat from the burner flame, and external terminal means extending through the wall of said casing opposite said closure member, and fusible means hermetically sealing the opening in said casing through which the terminal means extends.

6. An hermetically sealed switch assembly adapted for mounting within the blast tube of an oil burner comprising: an outer casing, an inner switch housing insertable into the casing. switching elements mounted within said housing, an electrically conductive member extending through a wall of said housing and electrically connected to said switch elements within said housing, electrical terminal deans extending through a wall of said casing adjacent said conductive member, and a flexible member extending between said terminal means and said conductive member and flexed an amount proportional to the depth of inser ion of said housing into said casing, said flexible member forming an electrically conductive path between said terminal means and saidconductive member which is independent of the insertion of housing into said casing to a precise given depth.

7. .An hermetically sealed switch assembly adapted for mounting within the blast tube of an oil burner comprising: an outer casing, an inner switch housing insertable into the casing, switching elements mounted within said housing, an electrically conductive member extending through a wall of said housing and electrically connected to said switch elements within said housing, electrical terminal means extending through a wall of said casing adjacent said conductive member, and a flexible member extending between said terminal means and said conductive member and flexed an amount proportional to the depth of insertion of said housing into said casing, said flexible member forming an electrically conductive path between said terminal means and said conductive member which is independent of the insertion of said housing into said casing to a precise given depth, and a mounting socket into which said casing is insertable, said mounting socket having receptacle means for accommodating said terminal means.

8. An hermetically sealed switch assembly adapted for mounting within the blast tube of an oil burner comprising: an outer casing, an inner switch housing insertable into the casing, switching elements mounted within said housing, an electrically conductive member extending through a wall of said housing and electrically connected to said switch elements within said housing, an electrical connector prong extending through a wall of said casing adjacent said conductive member, the inner end of said prong having an axial recess therein, a compression spring bottomed within said recess and contacting said conductive member when said housing is inserted into said casing, said spring being compressed an amount proportional to the depth of insertion of said housing into said casing and forming an electrically conductive path between said prong and said conductive member which is independent of the insertion of said housing into said casing to a precise given depth, and a mounting socket into which said casing is insertable, said mounting socket having receptacle means for accommodating said prong.

JUSTIN A. DEUBEL.

References Cited in the file of this patent UNITED STATES PATENTS 

